@JanusBahsJacquet Surely you mean that a dozen feet are four yards! Not sure what a ten of feet might be: probably some Hittite measure.
– tchrist♦Apr 10 '17 at 2:08

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Being in London may have triggered this interesting thought, but it surely has nothing to do with Britain as opposed to the US. The height of the Empire State Building, for example, would always be given in feet. The contemporary differences between British and US measurements are irrelevant to the question, as the Pilgrim Fathers brought this distinction between length-by-the-yard, height-by-the-foot (and much more) with them on the Mayflower. I'm afraid American exceptionalism won't answer this question.
– DavidApr 10 '17 at 18:18

4 Answers
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“Why, even though the yard an acceptable unit of distance, height is invariably measured in feet?” I find this question intriguing, especially as it appears that the yard was the dominant unit in measuring length as far back as the thirteenth century. To answer the question, then, one would appear to have to go back to mediaeval usage. In the absence of sources documenting the early use of the foot in measuring heights I shall present some observations and make a hypothesis.

Different units of measurement: some observations

They are important for, and reflect the needs of, trade and commerce.

They vary between trades or areas of activity — horses are measured in hands, race tracks in furlongs, chemists used to weigh in grains, farmers in bushels. Significantly, depth (with its relation to height) was measured in fathoms, rather than yards. Even today distances and speeds at sea are measure in nautical miles and knots!

A single measure was normally used, rather than the combination common today. For example, the Wikipedia entry on yard, quoted above, makes it clear that the introduction of ‘inches’ with yards was a legal measure to replace the black-market ‘handful’, rather than a response to a need to subdivide the unit. Halves and quarters of a single unit would be used.

A rationale for the choice of unit of measurement is that it should be small enough that one did not have to subdivide it into more than halves or quarters, and large enough that one does not have to use numbers containing more than two digits — it has to be usable by ordinary people.

The 13th century Statute of Ells and Perches standardization of the units of length was a response to local differences in usage (especially of the yard). It would be naive to think that local differences from the standard did not persist. If trade were local, this would hardly matter.

Height: a Hypothesis

My hypothesis is based on the premise that the commercial and practical need to measure height was much less than that to measure length — I can think of that might have been sold on the basis of height. I would suggest that the activity that required this, usage was architecture — probably civil/military, although perhaps also naval. Christopher Wren’s plans in the seventeenth century contain measurements in feet, and I suggest this is a continuation of practice that well may have been first adopted in Anglo-Norman times.

Why would architects have adopted feet, given that they were specifying length and breadth as well as height? One might argue that height was particularly important, and feet were already in use for measuring height. I do not know whether either of these assertions is true. An alternative is that the yard was much more ambiguous than the foot. Although the master builder may have adhered to the official standard, the workmen executing his plans might have had their own yard. Finally, it may have just been that the yard was too long for the detail required, and the foot and its half and quarter were more convenient.

It would be nice to know…

My hypothesis is difficult to prove, but it would be helpful to have more facts about the historical measurement of height:

How was height specified in the oldest historical documents in English that mention it? Was it indeed a concern — did people care about the exact height of a tall or small individual or of geographical features such as mountains?

What units are used in the oldest English architectural plans that specify them?

Am I right in saying that different units were not mixed? When were measurements first specified in a mixture of yards and feet, for example?

Footnote: Different meanings of the word ‘yard’ as a unit of measurement

According to the first edition of The Oxford English Dictionary (OED) ‘yard’, as used for a unit of length (and in several related meanings), is derived from a word which in different Germanic languages has the sense of pole, rod, prickle (and hence its obsolete use defined in OED-11 — “virile member, penis”). This is distinct from the origin of the word ‘yard’ with the general meaning of “inclosure” (sic).

As well as its equivalence (or that of the ell) to three feet, specified in the thirteenth century (OED–9, first example cited using the designation, ‘yard’, in 1377), another meaning of yard or landyard (OED–8) is given as “a unit of linear measure equal to 16½ feet…(but varying locally).” The OED cites a source as recent as 1856 which states “As a linear measure the yard varies considerably in different parts of the kingdom; at Hereford the landyard is 3 feet, at Saltash 16½ feet; at Falmouth and Bridgend 18 feet; and at Dowanpatrick 11 feet.”

A definition for this derivation of ‘yard’ in terms of area is also given in OED-10: “An area of land of varying extent according to the locality, but most frequently 30 acres” with usage dating back to 688–95.”

@Ily — I have added a footnote admitting that it has nothing to do with backyards. However, the section of the OED dealing with the word 'yard' as a unit of measure includes a documented meaning relating to area. Of course the OED may be wrong, and in any case I have not mentioned area in my revised text. However in the light of this you may wish to modify or withdraw your comment.
– DavidApr 10 '17 at 21:13

Well, of course, in some contexts the sense will be expanded to a square yard from the linear measure. No, its derivation still refers to the [stick > rod >] measuring rod used as the royal standard. You're right that downpage there's also a larger area unit that must derive from some old version of a surveyor's rod. Same point holds. That said, good on you for fixing your post and I'll switch to an upvote for the rest of the content.
– llyApr 11 '17 at 19:37

I'd edit the comment to note the point above (that I'm talking about the derivation of the term), but apparently the site's code won't let me.
– llyApr 11 '17 at 19:39

In the metric system, all distances are measured in meters, centimeters, millimeters, kilometers, etc., so you're not used to having different measures of distance used for different things.

In the U.S., we generally measure cloth in yards, but distances are usually measured in feet or miles, and heights are almost always measured in feet or miles. Depths of water used to be measured in fathoms. This is basically custom.

Similarly, in the U.S., liquid volumes are measured in gallons, but volumes of apples are measured in bushels.

Ah,but in American football distances are measured in yards. In fact, many sports traditionally use the yard as a distance unit.
– Hot LicksApr 8 '17 at 23:06

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@PeterShor: Personally, I think the yard isn't really a unit of measure, but rather a traditional compound unit (3 feet) used in specific conversations and activities, like the dime (10 cents) and C-note (100 dollars) and barrel (43 gallons).
– RickyApr 8 '17 at 23:25

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@Ricky - but so is the foot (12 inches) and the mile (5280 feet)
– JimApr 9 '17 at 0:52

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Ricky is getting upvoted but he's precisely wrong. The yard is and always has been the base unit of the English customary system.
– llyApr 9 '17 at 9:50

The 13th-century Act on the Composition of Yards and Perches notionally based the English measurement system on multiples of barley grains "dry and round" but going back to the Anglo-Saxons that's never how the system has worked. When money was involved, English measurements have always actually been derived from iron bars or other standards held by the king or from official copies.

The basis of all customary English length is the yard, although the Americans defined it in terms of the length of their stanard rod in meters in the 19th century and the Brits got around to following suit in the 20th.

As for why it worked out that way, it's because standard measuring of cloth was the most important commercial application early on and you need fairly long lengths for that. As for why don't we use yards to measure heights, it's because we measure our own heights in feet and inches and it's annoying to divide by three.

Could you provide a source for your statement that "The basis of all customary English length is the yard' and explain why you have inserted customary.
– DavidApr 9 '17 at 21:39

You directly contradict yourself here. You start out by saying that the yard is used for measuring height, and then later on you say, “As for why don’t we use yards to measure heights”, presupposing (as the question does) that it isn’t.
– Janus Bahs JacquetApr 10 '17 at 0:04

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@David: "customary English" is just the name for that measurement system. I think lly's statement is based on what is said in the linked Wikipedia article, "It is by international agreement in 1959 standardized as exactly 0.9144 meters." In other words, the current definition of units like feet and inches is derived from the definition of the yard, which is defined in terms of meters. I don't think this is the same sense of "base unit" as the question is using, though.
– sumelicApr 10 '17 at 0:12

@JanusBahsJacquet There's not a contradiction, so keep at it and you'll see it.
– llyApr 10 '17 at 14:41

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How exactly is “The yard is used to measure heights” followed by “We don’t use yards to measure heights” not a contradiction? Is someone other than ‘us’ (meaning, presumably, humans) going around measuring heights in yards? “It’s annoying to divide by three” also blatantly flies in the face of the very relational definition of yards and feet—and ignores the fact that it’s a lot more annoying to divide by twelve, which is what we do when we measure our own heights in feet and inches. Doesn’t answer why redwoods grow up to 379 feet tall, but not up to 126 yards tall.
– Janus Bahs JacquetApr 10 '17 at 14:50